This invention relates to a torque control for a fluid operated motor, and in particular, to a torque control operable to terminate the supply of fluid to the motor when the torque produced by the motor exceeds a predetermined level.
Fluid operated motors, such as air motors, are used to drive many devices such as wrenches, drilling equipment, screw drivers, tube expanders etc. In so driving such equipment, it is desirable to accurately limit the maximum torque supplied from the motor to the various devices to prevent damage to a work piece, or to the device. Further, it is desirable to immediately terminate the flow of fluid to the motor when the maximum torque is reached to insure that such maximum torque is not exceeded through inadvertent continued operation of the motor.
Heretofore, numerous mechanisms have been devised to accomplish the foregoing. However, most of the devices heretofore used employ either a friction device, or spring means to limit the maximum torque developed from a motor, or use various types of clutch mechanisms to disconnect the load from the motor when a predetermined maximum torque is obtained. Due to wear and rough handling, these devices are not accurate enough or do not remain accurate enough for fine tolerance work. Further, particularly in the instances wherein clutches are employed to disconnect the work from the motor, the clutches tend to wear quickly, thus increasing the maintenance cost involved in operating such motors.